Biopsy involves the sampling of the inner tissue of humans and animals for subsequent analyses and examination. Biopsy processes which are minimally intrusive are being increasingly used by doctors. Instead of using open surgery to cut off a piece of tissue for examination, physicians have been using needle mechanisms of various devices to obtain pieces of tissue without open surgery. Various manual devices have been used in the past. Many of these devices invariably had compartments that open and close in the tissue to be sampled, to entrap a piece of specimen. For example, the devices that have been used for the biopsy of prostate include the Veenema-Gusberg prostate biopsy cup, Franklin-Silverman biopsy needle (both manufactured by American V. Mueller), and the Travenol TRU-CUT biopsy needle. The Veenema-Gusberg prostate biopsy cup consists of a 0.5 cm diameter cup at the tip of the device. In operation, by opening and closing the cup after inserting it in the prostate, a piece of tissue is obtained by severing it and enclosing it. The Franklin-Silverman biopsy needle is used for the biopsy of kidney, liver, prostate, lymph gland, and thyroid tissues. It contains an inner split needle, the blade of which separates after entering the organ. The sheath is then advanced to close off the blades and to trap the specimen in the device. The most commonly used manual device is the Travenol TRU-CUT biopsy needle. The Travenol TRU-CUT biopsy needle consists of a notched stylet and a needle sheath. The Travenol mechanism operates by first advancing a stylet into the tissue, and then advancing a needle sheath over the stylet. A piece of tissue will then be trapped in the notch of the stylet as the stylet is retracted into the sheath, and can be retrieved for examination.
The aspiration method has also been used to obtain tissue samples for examination. The aspiration biopsy method operates by advancing a needle into the tissue to be sampled using a needle guide, and then using a syringe device to connect with the needle and aspirate samples into the needle. The advantage of the aspiration method is that fine (small diameter) needles can be used. The drawback is that only liquid samples, rather than a piece of tissue can be obtained, and one can only examine the cells in the liquid (cytology), while in pathology, both the cells and the structure are examined. Since the aspiration method is much less intrusive than other known sampling methods, it is less painful to the patient, and has fewer side effects. That is because the smaller the biopsy needle or instrument, the less likely it is to cause complication and pain.
In recent years, mechanical devices have been designed and combined with biopsy devices to provide quicker action and a cleaner cut of a tissue specimen. The basic principle behind these devices is that a cleaner, more precise cut can be made by utilizing a mechanical or electro-mechanically driven device, rather than the one controlled by the human hand. These spring-loaded biopsy devices such as those found in U.S. Pat. Nos. 4,776,346; 4,702,261; 4,699,154 and 4,917,100 generally utilize needles with a biopsy mechanism similar to that of the Travenol TRU-CUT biopsy needle.
Although the use of a spring-loaded biopsy device has advantages over the use of manual devices, the use of these biopsy mechanisms still poses certain limitations of the previously referred to notch type biopsy devices. For example, it is necessary for the size of the biopsy needle to be of a relatively large caliber to allow for a notch therein that is capable of obtaining a specimen large enough to enable proper testing. The size of the notch in turn is limited by the size of the overall device in an effort to make the biopsy procedure as noninvasive as possible. Since the solid portion of the stylet occupies a significant portion of the lumen, the size of the tissue obtained is considerably smaller than the diameter of the needle. Since the needle is fired under a mechanical force, the needle must also have sufficient strength and therefore size especially in the narrowed notch area, so that there is no significant risk of breaking the needle during the process. This specimen is sometimes too small for adequate examination and therefore requires the invasive biopsy procedure to be repeated until a sufficient sample is obtained.
In the present invention when a tissue sample is taken, the stylet does not remain in the section of the biopsy lumen that retains the tissue sample obtained from the biopsy at the end of the procedure. Thus, the full lumen of the biopsy needle can be filled with the specimen. The present invention therefore can provide an equal or larger size of specimen by using a significantly smaller sized needle than prior known devices. A smaller sized needle is less invasive and therefore likely to cause less pain and fewer complications.
Furthermore, in a biopsy needle that contains a notched stylet, the notched portion is usually the thinnest and weakest portion. This type of structure can be potentially dangerous when the needle encounters resistance to its travel. When it is fired with a spring-loaded device, the stylet part can bend or even break, which can cause very serious complications. These factors further limit how small a biopsy needle can be made. For these reasons, most physicians do not use current devices for deep organ biopsies and for lesions adjacent to large blood vessels. The: present invention, which uses no notched stylet and has the capacity to obtain larger sized tissue samples with a smaller sized, structurally stronger needle, also provides a greater variety of uses as a result.